Scientists discover new DNA base

It was long believed that DNA, the genetic material of all living things, was made up of four basic units or “letters,” know as A, C, G and T (adenine, cytosine, guanine and thymine). These units pair up, A with T and C with G, to form long, readable sequences responsible for making us who we are.

Another unit, 5-methylcytosine (mC), was then discovered in the 1980s, which is cytosine but with a functional unit called methyl attached. As stated in a recent article, the addition of methyl groups to DNA can switch genes on or off in order to meet the needs of each tissue, given that every cell contains the same DNA sequence.

Such modifications are known as epigenetic changes and allow the environment to affect gene expression, which plays a role in various diseases. For example, alterations in mC have been shown to contribute to the development of cancer, among many other conditions, the article states.

The knowledge around DNA did not stop there and over the years, scientists expanded the DNA alphabet to eight characters. However, now, a new study recently published in the journal Cell, details another unit known as N6-methyladenine (6mA). The article states that as with mC, this unit is composed of the base adenine with a methyl group tacked onto it. What’s interesting, is that scientists believed that it exclusively existed in bacteria, where it protects against the unwanted addition of foreign DNA from other organisms.

However, scientists have found this is not the case. Evidence from the study shows that 6mA is not simply a phenomenon of primitive cells. As described in the article, scientists found that some more complex cells, called eukaryotic cells, also possess the base. Eukaryotes are organisms within one of the three domains of life, the others being archaea and bacteria.

More specifically, researchers discovered 6mA in three different groups of eukaryotes: green algae, flies and worms. As stated in the article, this was made possible through the development of highly sensitive analytical techniques, which picked up the exceedingly low levels of this base that previously eluded detection. Newly gathered data indicates that, like mC, 6mA may also have a gene regulatory function in these animals, which could suggest that it also behaves as an epigenetic mark.

So why is this important? Now that scientists have found this base in various organisms, researchers want to scrutinize human genomes to see if it also exists in us. This would be interesting given the fact that evidence seems to suggest that 6mA may play a role in stem cells.

The articles goes on to say that if it does indeed exist in our own species, researchers will then have to figure out what precise role it plays in our cells.